1. Field of the Invention
This invention relates to a very strong and highly active titanium trichloride catalytic component for polymerization of an .alpha.-olefin which permits adjustment of the average particle diameter thereof to a value between 10 and 500.mu. as desired and has a high degree of uniformity of the particle diameter and a method for homo- or co-polymerization of an .alpha.-olefin which is carried out in the presence of a catalytic combination of the above stated titanium trichloride catalytic component and an organo-aluminum compound to obtain a polymer product having a highly uniform spherical particle shape. More particularly stated, the invention relates to such catalytic component and a method which either dispense with or simplify deashing and washing processes generally necessitated in the manufacture of an .alpha.-olefin polymer; facilitate the gas-phase polymerization of an .alpha.-olefin or propylene in particular which has been considered difficult; and obviate the necessity of a pelletizing process in the manufacture of the polymer.
2. Description of the Prior Art
There have been proposed many and various methods for obtaining a titanium trichloride catalytic component that has a high polymerization activity and is capable of enhancing productivity for a stereospecific polymer. However, almost all of the catalytic component obtainable by the manufacturing methods of these prior arts are in a powdery state having uneven particle sizes. Accordingly, the polymer obtained from the use of such a catalytic component has been in a powdery state and has caused troubles in manufacturing processes because it is difficult to separate, dry and transport. Further, the polymer obtained from the use of such a catalytic component has necessitated pelletization through melting, kneading, extruding and shaping processes after drying and before the polymer product thus obtained is supplied to molding and machining fields. An .alpha.-olefin polymer manufacturing plant thus has required a great amount of cost of facilities for the pelletizing processes consuming a great amount of energy and lowering the productivity of the plant. Thus, these conventional titanium trichloride catalytic components have many shortcomings. If it is possible to obtain a catalytic component which permits polymerization to obtain a polymer that has a highly uniform particle diameter without including any fine granular polymer therein, such a catalytic component not only would enhance the operation efficiency of a polymer manufacturing plant but also would completely obviates the necessity of such an additional process of pelletizing the polymer produced. Then, such a catalytic component would immensely contribute to the rationalization of the polymer manufacturing processes of the plant. Therefore, development of such an ideal catalytic component has been strongly desired.
There have recently been developed some granular catalytic components which have a high polymerization activity and permit to obtain stereospecific polymers at a high rate of productivity. For example, a Japanese patent application laid-open No. 47-34478 discloses a method for obtaining a .delta.-type titanium trichloride of a dark purple color and a granular shape. In that method a .beta.-type titanium trichloride is obtained by reducing a titanium tetrachloride at a low temperature with an organo-aluminum compound; the .beta.-type titanium trichloride is treated with a complexing agent; and then the trichloride is subjected to a heating treatment in a titanium tetrachloride. Further, Japanese patent applications laid-open No. 51-16298, laid-open No. 51-76196 and laid-open No. 53-12796 also disclose a method of obtaining fine granular solid titanium trichlorides through a liquid matter, which is obtained by treating a titanium tetrachloride with an organo-aluminum compound in the presence of an organic ether compound, into contact with a liberating agent such as Lewis acid or the like at a temperature below 150.degree. C.
The catalytic component obtainable by such methods is an excellent catalytic component having a high polymerization activity. However, the average particle diameter of the titanium trichloride catalytic component thus obtained is 30 to 40.mu. at the most. Particularly, the particle size of the titanium trichloride catalytic component obtainable by the latter method is still too small and the catalytic component is difficult to handle because of its poor fluidity and its small bulk density. When an .alpha.-olefin is polymerized by using such a catalytic component, a polymer thus obtained also has small particle diameter and small bulk density. Besides, the use of such a catalytic component not only results in a low productivity for obtaining a stereospecific polymer but also necessitates a pelletizing process because it is in a powdery state.
A method of reducing a titanium tetrachloride with an organo-aluminum compound in the presence of an olefin also has been proposed by another Japanese patent application laid-open No. 52-142691. The subject matter of this prior art lies in that: in reducing the titanium tetrachloride with the organo-aluminum compound, a titanium trichloride is allowed to separate while a slight amount of propylene is supplied during the reducing process; and then a further treatment is carried out with a complexing agent and the titanium tetrachloride. However, a catalyst obtained from a combination of a titanium tetrachloride and an organo-aluminum compound is known by the name of a Ziegler catalyst and has been in use as catalyst for polymerization of an olefin. Judging the above stated prior art from this knowledge, it seems that a low molecular weight olefin polymer produced by the use of the titanium tetrachloride and the organo-aluminum compound comes to serve as binder to cause a separated titanium trichloride to coagulate into a coagulated titanium trichloride. Therefore, it is believed that, in accordance with this method of the prior art, the particle diameter of the titanium trichloride cannot be made smaller though it can be made larger. This has been also found in an experiment which will be described hereinafter as reference example.
Meanwhile, the present inventors have previously proposed a titanium trichloride catalytic component which has a high polymerization activity and a high productivity for obtaining a stereospecific polymer and which permits to control as desired its particle diameter and eventually to control as desired the particle diameter of the olefin polymer to be obtained therefrom and, thereby, which obviates the necessity of a pelletizing process and a method of carrying out a homo- or co-polymerization of an .alpha.-olefin in the presence of a catalyst consisting of the titanium trichloride catalytic component and an organo-aluminum compound as disclosed in Japanese patent applications laid-open No. 54-90094 and laid-open No. 55-3456. The inventors have further studied for a method of manufacturing a titanium trichloride which has a great strength. As a result of the study, they have discovered that, in the process of allowing a titanium trichloride to separate, an arrangement to carry out the process in the presence of an .alpha.-olefin gives a titanium trichloride catalytic component which is of a small particle diameter between 2/3 and 1/2 of the catalytic component obtainable without having any olefin present during the separating process and which greatly excells in strength. This discovery has led to the present invention. Judging from the fact that there exists several percent of an olefin polymer in the titanium trichloride catalytic component, this phenomenon probably results from that the polymer serves to solidify the particles of the catalyst in such a way as to make the particles smaller and, at the same time, to make them stronger. This is a wonderful fact hardly expectable from the prior arts.